Gliomas are primary malignant tumors, originating in the brain, and account for 80% of adult primary brain tumors. Malignant gliomas which includes glioblastoma are the most common and fatal intracranial tumors (Furnari, F. B.; Fenton, T.; Bachoo, R. M.; Mukasa, A.; Stommel, J. M.; Stegh, A.; Hahn, W. C.; Ligon, K. L.; Louis, D. N.; Brennan, C.; Chin, L.; DePinho, R. A.; Cavenee, W. K. Malignant astrocytic glioma: genetics, biology, and paths to treatment. Genes Dev 2007, 21, 2683-710). The prognosis for patients with glioblastoma multiforme, a virulent variety of the disease is rather poor, with a median survival of less than one year (Legler, J. M.; Ries, L. A.; Smith, M. A.; Warren, J. L.; Heineman, E. F.; Kaplan, R. S.; Linet, M. S. Cancer surveillance series [corrected]: brain and other central nervous system cancers: recent trends in incidence and mortality. J Natl Cancer Inst 1999, 91, 1382-90). One of the most important challenges we face today is to develop novel methods of therapy. Several altered genes and pathways have been target of designing novel therapeutic strategies. Inventors had earlier reported PBEF1/NMPRTase/Visfatin as a potential malignant astrocytoma/glioblastoma serum marker with prognostic value (Reddy, P. S.; Umesh, S.; Thota, B.; Tandon, A.; Pandey, P.; Hegde, A. S.; Balasubramaniam, A.; Chandramouli, B. A.; Santosh, V.; Rao, M. R.; Kondaiah, P.; Somasundaram, K. PBEF1/NAmPRTase/Visfatin: a potential malignant astrocytoma/glioblastoma serum marker with prognostic value. Cancer Biol Ther 2008, 7, 663-8). PBEF1 transcript and protein levels were found to be elevated in malignant gliomas, in particular glioblastoma tissue samples and also in the corresponding patients serum samples (Reddy, P. S.; Umesh, S.; Thota, B.; Tandon, A.; Pandey, P.; Hegde, A. S.; Balasubramaniam, A.; Chandramouli, B. A.; Santosh, V.; Rao, M. R.; Kondaiah, P.; Somasundaram, K. PBEF1/NAmPRTase/Visfatin: a potential malignant astrocytoma/glioblastoma serum marker with prognostic value. Cancer Biol Ther 2008, 7,663-8). PBEF1 encodes
Nicotinamide phosphoribosyltransferase (NMPRTase), which catalyses the rate limiting step in the salvage pathway of NAD (Nicotinamide Adenine Diphosphate) metabolism in mammalian cells. While the role of PBEF1 over expression in glioma is not understood, it may regulate signaling pathways related to apoptosis and chemosensitivity (Jia, S. H.; Li, Y.; Parodo, J.; Kapus, A.; Fan, L.; Rotstein, O. D.; Marshall, J. C. Pre-B cell colony-enhancing factor inhibits neutrophil apoptosis in experimental inflammation and clinical sepsis. J Clin Invest 2004, 113, 1318-27; Yang, H.; Yang, T.; Baur, J. A.; Perez, E.; Matsui, T.; Carmona, J. J.; Lamming, D. W.; Souza-Pinto, N. C.; Bohr, V. A.; Rosenzweig, A.; de Cabo, R.; Sauve, A. A.; Sinclair, D. A. Nutrient-sensitive mitochondrial NAD+ levels dictate cell survival. Cell 2007, 130, 1095-107; Folgueira, M. A.; Carraro, D. M.; Brentani, H.; Patrao, D. F.; Barbosa, E. M.; Netto, M. M.; Caldeira, J. R.; Katayama, M. L.; Soares, F. A.; Oliveira, C. T.; Reis, L. F.; Kaiano, J. H.; Camargo, L. P.; Vencio, R. Z.; Snitcovsky, I. M.; Makdissi, F. B.; e Silva, P. J.; Goes, J. C.; Brentani, M. M. Gene expression profile associated with response to doxorubicin-based therapy in breast cancer. Clin Cancer Res 2005, 11, 7434-43). A potent inhibitor of NMPRTase enzyme, FK866, has been shown to reduce cellular NAD+, inhibit growth of PBEF1 over expressing cells and induce apoptosis in tumors (Hasmann, M.; Schemainda, I. FK866, a highly specific noncompetitive inhibitor of nicotinamide phosphoribosyltransferase, represents a novel mechanism for induction of tumor cell apoptosis. Cancer Res 2003, 63, 7436-42). The crystal structures of free NMPRTase, NMPRTase bound to NMN, and NMPRTase bound to the inhibitor FK866 have recently been reported (Khan, J. A.; Tao, X.; Tong, L. Molecular basis for the inhibition of human NMPRTase, a novel target for anticancer agents. Nat Struct Mol Biol 2006, 13, 582-8). FK866 is a potent small-molecule inhibitor of human NMPRTase, and the consequent reduction in NAD levels can cause apoptosis of tumor cells while having little (toxic) effects on normal cells (Hasmann and Schemainda, 2003). FK866 also turns out to be the only promising inhibitor known, for the enzyme. The available structures provide a basis for understanding substrate specificity, mechanism of enzyme action and provide a framework for design of novel NMPRTase inhibitors.
Here inventors report virtual screening of a large library of compounds and short listing of 6 candidate molecules that are likely to bind to NMPRTase. These compounds were subsequently tested experimentally for their ability to (a) inhibit the conversion of Nicotinamide to NAD by NMPRTase and (b) inhibit efficiently the growth of NMPRTase over expressing glioblastoma derived cell line U87. Based on these studies, a promising lead compound has been identified.
Currently there are only few compounds known to inhibit NMPRTase activity. So it is essential to search for more potential compounds for glioblastoma therapy.
Using Bioinformatics approach, the inventors screened 13214 compounds to identify possible candidates as inhibitors for NMPRTase enzyme, and found, 3-amino-2-benzyl-7-nitro-4-(2-quinolyl)-1,2-dihydroisoquinolin-1-one as a promising lead compound that inhibits NMPRTase and glioma cell growth.